1. Field of the Invention
This invention relates broadly to eye surgery. More particularly, this invention relates to refractive laser systems for eye surgery.
2. State of the Art
The excimer laser refractive surgery field has exploded over the past few years with many new lasers systems to correct human vision. These systems use an ultraviolet excimer laser to change the shape of the cornea in a calculated pattern which makes it possible for the eye to focus properly. For example, in the treatment of myopia, the laser is used to remove tissue from the cornea in order to flatten its shape. The correction of hyperopia is produced by steepening the cornea. The correction of astigmatism requires the laser to remove tissue in a more complex pattern. All of these procedures require precise shaping of the cornea which depends on accurate placement of the laser beam. Therefore, any eye movement can affect the placement of the laser beam.
Most currently approved broadbeam refractive laser systems and scanning spot systems do not incorporate eye tracking. Therefore, the patient is required to minimize eye movement during surgery by voluntarily fixating their eyes on a small light located just above the patient. When the average person fixates on something, he or she has about five saccadic eye movements per second. Saccadic eye movements are rapid, involuntary movements that are random in amplitude and direction. These movements can cause eccentricity of the laser beam, resulting in degraded laser vision correction predictability and visual quality.
Newer generation refractive laser systems that use small scanning spots, usually less than 1 mm in diameter, have implemented eye-tracking techniques that move the laser beam to adjust for eye movement. Early indications suggest that this approach provides a higher accuracy ablation by virtually eliminating shaping error caused by eye movement.
Nevertheless, there already exists a large number of broadbeam and scanning spot systems which are not provided with eye tracking capability. There is currently no available means by which to provide existing systems with eye tracking capability.